Your entire cooling system may need replacement soon. BMW is notorious for this problem around 100k miles, I did a cooling system overhaul on my e46 way before 100k and haven't looked back. I think it was roughly ~$400 from ECS Tuning for all the parts.
2000 ///M5 ///M Registry
Oxford Green Metallic II (430) | Caramel Nappa Leather (M3CR) | BMW Individual Black Birch |
Tuning Tech Tune by Frank Smith (http://www.tuningtechfs.com/)
Storm Motorwerks Products
2011 X5 35d | Alpine White | Beige | Sports Pkg | Premium Pkg | Cold Weather Pkg | 3rd Row
2003 X5 4.6iS | Black Sapphire Metallic | Black Sport | DINAN Software | FOR SALE!